It's a bona fide C++ killer for applications that are both security and performance critical. It's already gaining traction for those applications even within relatively conservative engineering organisations.
That said, there are many performance-critical applications who are not security-critical, and in those I'd expect C/C++ to persist pretty much indefinitely. And many security-critical applications which are not performance-critical, and can perfectly well be served by garbage collected languages like Java/C#/Go.
Cargo is the problem for those organizations. People who worry about security and safety often develop on airgapped networks. You can go nostd for small stuff. For bigger stuff you could mirror crates.io but that isn't a well supported workflow and it's a lot o code from a lot of randos. The notion of a blessed subset would help get more buy in from that community. Even still, rustup isn't working on airgapped Dev nets and it's a nice feature especially if you are crosscompiling.
I don't like GC (on an ideological level), but I still write most stuff in Go because I'm so insanely productive in it. Will probably use more Rust once async/await is there and mature enough.
C++ has a huge learning curve too though, the difference is it lets you write whatever you want. The learning curve is to write correct C++. It’s deceptive, it’s like skiing vs snowboarding. Skiing you pick up fast but to get good is damn hard and few bother. Snowboarding is damn hard to pick up but then it’s pretty easy to become really good.
To modify this I'd say that becoming reasonably good is pretty easy (and I'd agree easier than skiing). To be become really good takes a long time and a lot of dedication and the difference in difficulty between skiing and snowboarding disappears. Same as with programming, some languages make it easier to go from 0 to your first app, some make it easier to write solid production ready code that earns you a paycheck, but becoming really good is always hard and independent of the language you're using.
> Rust's learning curve isn't exactly a shallow one either.
I don't know how people can be so sure of this. We know essentially nothing about how to teach or learn Rust effectively, it's something that the community is just starting to look at. However, one thing we do know is that the detailed support that the Rust compiler provides to the novice programmer is quite simply unparalleled in other mainstream languages. It's basically the ultimate T.A.
I’m not sure I’d use as strong language as you (though I personally love the rust compiler’s messages), but I will say it’s gotta count that it doesn’t automatically and silently generate instance methods that explicitly break the memory model (cough rule of three…)
For the record I think Rust has a lot going for it, but it is not the C++ killer that many are touting it to be.